There is a need for a technique by which the spectral sensitivity of the green short wavelength region in a silver halide color photographic photosensitive material can be raised and by which the color reproduction of the photosensitive material can be improved.
Known techniques for increasing the spectral sensitivity of the green wavelength region include photographic emulsions in which conventional oxacarbocyanines and benzimidazolocarbocyanines are used conjointly (for example JP-A-59-116646, JP-A-59-116647, JP-A-59-140443 and JP-A-59-149346), in which oxacarbocyanines and oxathiacarbocyanines are used conjointly (for example, JP-B-46-11627 and JP-A-60-42750), and in which two or more oxacarbocyanines are used conjointly (for example JP-A-52-23931). But in all these cases, the spectral sensitivity of the green short wavelength region of 520 to 545 nm is low and difficulties arise with color reproduction. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application", and the term "JP-B" as used herein signifies an "examined Japanese patent publication".)
The conjoint use of sensitizing dyes which have a spectral sensitivity peak in the range 520 to 545 nm has also been considered. However, in the past benzimidazolooxazolocarbocyanine (for example JP-B-44-14030) and dimethinemerocyanine (for example U.S. Pat. Nos. 2,493,748, 2,519,001 and 3,480,439) were known as sensitizing dyes which had a spectral sensitivity peak value of not less than 520 nm and less than 545 nm. But with emulsions to which benzimidazolooxazolocarbocyanine or dimethinemerocyanine have been added, the fog level increases at elevated temperatures or under conditions of high temperature and high humidity after the emulsion has been coated. Or there is a worsening of the ageing stability and a loss of photographic speed after the emulsion has been coated. It is therefore thought that the conjoint use of these compounds is inappropriate.
Furthermore, the oxacarbocyanines, for which the problems described above are minor, have a spectral sensitivity peak value of 520 to 545 nm and have been disclosed for example in U.S. Pat. Nos. 2,521,705, 2,521,959 and 2,647,054 and in JP-A-63-167348. But the spectral sensitivity of these dyes is inadequate. Furthermore, a mono-methinecyanine which includes a 2-quinoline skeleton has a spectral sensitivity peak value of 520 to 545 nm. But when they are used individually, photographic speed is low and so they are used conjointly with benzoimidazolocarbocyanine and oxacarbocyanine (for example JP-B-56-24939, JP-B-56-38936, JP-B-56-38940 and British Patent 1,219,016). However, when they are used conjointly in this way, the spectral sensitivity region is inevitably shifted to a longer wavelength and so good color reproduction cannot be obtained. Hence, a technique for increasing spectral sensitivity in the green short wavelength region is required for obtaining faithful color reproduction with a color photosensitive material.